Loans and Related Allowance for Credit Losses (Financial Impact and TDRs by Concession Type) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) loan	Mar. 31, 2021 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	2,907	2,115
Pre-TDR Amortized Cost Basis	$ 89	$ 125
Post-TDR Amortized Cost Basis	79	122
Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	26	16
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	$ 53	$ 106
Total commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	12	19
Pre-TDR Amortized Cost Basis	$ 53	$ 93
Post-TDR Amortized Cost Basis	46	94
Total commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	$ 46	$ 94
Total consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	2,895	2,096
Pre-TDR Amortized Cost Basis	$ 36	$ 32
Post-TDR Amortized Cost Basis	33	28
Total consumer | Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	26	16
Total consumer | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	$ 7	$ 12